The present invention generally relates to web processing apparatus and methods for slitting a wide web of material into plural web portions and subsequently winding the web portions into separate rolls. In particular, the web material is initially slit while leaving connections between the web portions and breaking the connections prior to winding.
In some situations, it is desirable to split a single, relatively wide web of material into a plurality of relatively narrow web portions and wind the web portions into several rolls (or otherwise convert the web portions into use supply forms). It is generally more efficient to produce and/or process material in wider webs but often more convenient to package, ship, sell, and/or use the material in narrower rolls. Also, the narrower web portions are preferred or required for some applications. Common examples of web materials that are often split into web portions include paper (for example, toilet paper, computer paper, paper towels, etc.) and tape (for example, adhesive tape, magnetic tape, etc.). Slitting can be done on single webs (for example, films), structured webs (for example, webs with structured features), multilayer laminates, or coated webs (for example, adhesive coated webs for making adhesive tape).
A plurality of web portions can be formed from a web by slitting (or otherwise cutting) the web in the lengthwise direction so that the individual web portions are separated from one another. U.S. Pat. No. 3,695,131 issued to Zimmermann relates to one such approach wherein a web is carried by a traveling support surface across razor sharp cutting edges of circular slitting blades, wherein the web is held on the traveling support to reduce longitudinal or transverse shifting of the web portions. The slitter blades are rotated so as to distribute wear uniformly about the circumferences of the slitter blades. After slitting, the various web portions are directionally separated by directing adjacent web portions through different guide means that thread the web portions to different winding reels.
U.S. Pat. No. 2,897,893 issued to Rockstrom et al. relates to another slitting mechanism in which a continuous web of material is taken from a mill roll and passed over a compensating roll in a rewind machine and under a cutter roll against which the web is slit into web portions before winding into a rewind roll. Slitting wheels bear against a hardened sleeve of the cutter roll at any desired position along the sleeve and they bear with sufficient pressure to sever the web into web portions. The slitting wheels are softer than the hardened sleeve and, although preferably not given a sharp edge, they divide the web. Immediately after the web is cut by the slitting wheels, an angular-faced spreader having a vertical, forward-extending center with backswept sides bears against the web with the forward center of the spreader bearing on the line of the cut to push the web portions apart and to assure their complete separation along the cutting line. U.S. Pat. No. 1,465,967 issued to Cameron et al. relates to a somewhat similar slitting and rewinding machine that also includes a secondary separating device having a knife blade for severing any stray fibers connecting adjacent web portions that have not been severed by the slitting action. The secondary separating device severs the stray fibers after slitting and before winding of the web portions.
After the plural web portions are split and separated, they typically pass individually through guiding and tensioning rollers and then are ultimately wound about a core to form a roll of web material. Each web portion may be individually guided to a distinct core, or plural cores can be supported in axial alignment on a single shaft. Often, adjacent web portions are divided to different winding shafts supporting such plural cores so that they can be guided without interfering with one another. Alternatively, the plural web portions can ultimately be folded, cut, or otherwise processed to form a stack (or other form) of web material. The roll or stack of web material is the use supply form that is used by the consumer of the web portions. To process the split, separated web portions to create use supply forms, each web portion must be individually guided, which requires accurate control to prevent each web portion from wandering. Tension control is an important aspect of web guiding, and web properties (such as the thickness of the web across the web) can cause slight variations in guiding and tensioning each web portion. Variations in guiding and tensioning can cause the web portions to wander and be wound with uneven edges and, where several rolls are wound side by side about a common winding shaft, to be wound with overlapping and interweaved edges that cause the several rolls to become intermeshed.
It is also known to perforate web or web portions prior to forming the use supply forms in order to provide a perforation or tear line so that someone or something provided with the web material in use supply form can split the web material by tearing along the perforations. The perforation or tear line is formed by cutting a plurality of small, spaced slits in the web material. The connections of the web material that remain between the slits maintain the structural integrity of the web material until the connections are torn to further separate the web or web portion along the perforation line. A number of different configurations of perforations lines have been developed.
Perforations can be created in the machine direction of a web or web portion by a perforating wheel having a beveled cutting edge in which one or more notches are formed at angularly spaced intervals so as to define cutting and non-cutting portions of the cutting edge. Typically, several perforating wheels are spaced and rotatably mounted along a bar so that the perforating wheels tangentially contact the outer surface of a back-pressure roll, which is rotated by a motor or the like. The rotation of the back-pressure roll causes the perforating wheels to rotate. The web is run between the perforating wheel and the back-pressure roll and, as the perforating wheels rotate and the cutting portions of the cutting edges come into contact with the web, the cutting portions of the cutting edges penetrate and cut the web to form the perforations. When the perforating wheels further rotate and the non-cutting portions move over the web, the notches formed in the cutting edges prevent the web from being cut, which forms the connections in the perforation line. A perforating wheel of this general type is disclosed in U.S. Pat. No. 3,978,753 issued to Meaden et al. Thus, perforations can be provided in the longitudinal direction so as to define two or more connected web subportions that are wound or stacked into the use supply form.
Perforations can be provided across the transverse width of the web or web portion so as to define individual sheets of the web material. Examples include paper towels and toilet paper, which are typically perforated so that individual sheets can be separated from the roll by the consumer. Many techniques have been developed to make transverse perforation as a web is moved in a machine direction. Most rely on a perforating roll that creates the perforation lines at spaced intervals on the web based upon a notched cutting edge extended transversely on the roll. Whether longitudinally or transversely perforated, such connected web subportions are designed to be separated by a consumer as the web material is converted from its use supply form.
One noteworthy application of perforations in web or web strands is in continuous paper of the type commonly used in computer printers, especially contact or dot matrix type computer printers. Continuous paper of this type is commonly sold as a stack or roll of paper having rows of perforations across the width of the paper. The spacing of the these rows determines the length of the page. Typically, the paper is folded along the perforations alternately in opposite directions, resembling a fan or accordion. Such continuous paper can be moved past a printer mechanism of a printer using a friction feed mechanism that pinches the paper between two rollers, one of which is typically driven by a motor. However, when more than a few pages are printed using only a friction feed mechanism, the continuous paper tends to wander out of alignment.
One solution to the wandering problem adapted for contact or dot matrix type computer printers involves the use of a tractor feed mechanism in which sprockets engage holes in special computer paper. The computer paper is continuous as described above but also has a narrow guide strip on each side along the length of the paper. The guide strips have a plurality of regularly spaced holes for engaging the sprockets in the tractor feed mechanism to advance the paper. Each guide strip is typically separated from the sheet by perforations that define tear lines.
Although the pages of a printout (the printout being computer paper on which the printer has printed) are sometimes left joined together end to end, the guide strips on the sides are usually removed. Because removing the guide strips after the paper has exited the printer can be time consuming (for example, if the guide strips are removed page by page) and/or can damage the paper (for example, if the guide strips are removed from several sheets of folded paper at once), several approaches to separating the guide strips from the paper immediately after printing but before the paper exits the printer have been developed. For example, U.S. Pat. No. 5,259,543 issued to Downing relates to a parting tool that can be attached to a tractor feed mechanism for separating the guide strips from computer paper as the paper passes through the tractor feed mechanism. The parting tool includes a blade intersecting the plane of the paper for shearing the paper along the perforations connecting the guide strips to the sheets of paper.
The continuous and computer papers described above are provided to the consumer in use supply form with perforations provided in the web material in its use supply form. Separation of the perforations occurs, if ever, at or after use by the consumer. In other words, the perforations are not separated in the process of making the use supply form.
The present invention relates to an apparatus and method of converting a web of indefinite length into a plurality of web portions by slitting the web at at least one transverse point prior to processing the web portions into a plurality of use supply forms (such as rolls), wherein the plurality of web portions are separated by a two-stage process. Preferably, the converting process is continuous in a machine direction of travel by the web. A first stage of the process is a partial separation operation that almost entirely separates the web portions, but leaves the web portions connected, such as by a slitting operation that leaves a series of connected zones. The second stage includes the complete separation, such as by breaking of the connected zones. The complete separation of the web portions preferably occurs near the station at which the use supply forms are created, such as a winding station. Thus, the web portions, after substantial separation at the first stage can be handled (for example, guided and tensioned) as if the plurality of web portions were a full width web. But, after handling and transporting of the web portions to the use supply form station, the web portions are completely split so that the plural web portions can be wound or otherwise converted into a plurality of use supply forms. By handling and transporting the plurality of substantially split web portions as a fall width web, the handling and transporting of each of the web portions separately and the possible resulting variations in guiding and tensioning that can lead to wandering and other problems can be avoided.
One aspect of the present invention is a method of converting a web having a transverse width and of indefinite length into plural use supply forms as the web is moved in a machine direction by slitting the web into plural web portions of indefinite length. The method comprises supplying a web having a transverse width and of indefinite length and transporting the web in a machine direction. The method also includes moving the web through a first separation stage and thereby partially separating the web at a point along its transverse direction for making a partially separated web and defining connected web portions running in the machine direction of the partially separated web. In addition, the method includes transporting the partially separated web from the first separation stage to and through a second separation stage and thereby separating the connected web portions into discrete web portions, and converting the discrete web portions into use supply forms thereof.
Another aspect of the present invention is an apparatus for converting a web having a transverse width and of indefinite length into plural supply use forms by moving the web in a machine direction and slitting the web into plural web portions of indefinite length. The apparatus comprises a source of a web having a transverse width and of indefinite length and transport means for moving the web from said source in a machine direction. The apparatus also includes a first separation stage located downstream from the source and comprising a first separation device that partially separates the web at a point along its transverse direction and makes a partially separated web having defined connected web portions that extend in the machine direction of the partially separated web. In addition, the apparatus includes a second separation stage located downstream from the first separation stage and comprising a second separation device that separates the connected web portions into discrete web portions, and a use form conversion station for converting the discrete web portions into use supply forms.